Heretofore, viscous polysaccharides have been widely used for their properties of thickness and viscosity as additives for foods and cosmetics. Utilities as an adhesive, coating agent, freezing stabilizer, lubricating agent, additive for drilling mud, enhanced oil recovering agent, etc., have also been developed. Recently, it has been found that certain polysaccharides have pharmacological activity, such as anti-tumor activity, hypotensive activity, etc. Therefore, an increase of their use as drugs is expected.
It is well known that certain microorganisms produce polysaccharides. For example, strains of genera Alcaligenes, Bacillus, Xanthomonas, Arthrobacter, Azotobacter, Pseudomonas, Leuconostoc, Aureobasidium, etc., produce polysaccharides.
Further, it is also known that certain strains of genus Acetobacter produce polysaccharides, for example, cellulose from Acetobacter xylinum (Biochem.J., 58, 345 (1954)), levan from Acetobacter suboxydans (Tr. Petergof. Biol. Inst. Leningrad. Gos. Univ., 19, 20 (1965)), and dextran from Acetobacter capsulatum (J. Biol. Chem., 192, 161 (1951)). It was also reported that a nitrogen-containing polysaccharide composed of glucose, mannose, rhamnose and glucuronic acid was isolated from a spontaneous mutant of Acetobacter xylinum (Can. J. Microbiol., 27, 599 (1981)).